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Wang Z.-G.,Yancheng Institute of Technology
Applied Mechanics and Materials | Year: 2013

Stepped distributed dynamic systems are widely used in the engineering fields, and the dynamic characteristics analysis of them is very important. In this paper, the axial vibration of a stepped bar consisting of two uniform sections is studied, in order to solve the dynamic equation, the differential transformation method is used, the governing differential equation and the boundary conditions of the bar become simple algebraic equations. Doing some simple algebraic operations for these equations, the closed form solution of natural frequency, mode shape and the dynamic response can be obtained. Comparison the results obtained by the differential transformation method and finite element method, excellent agreement is achieved, and the effects of the stiffness of spring is discussed in this paper. © (2013) Trans Tech Publications, Switzerland. Source

Yao Z.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Yao Z.,Yancheng Institute of Technology | Xiao L.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion
IEEE Transactions on Power Electronics | Year: 2012

Renewable energy sources, such as solar energy and fuel cells, are desirable due to their pollution-free properties. In order to utilize the present infrastructure of the utility grid for power transmission and distribution, grid-connected inverters are required for distributed generation systems, which should have high reliability. However, a shoot-through problem, which is a major deterrent to the reliability of the inverters, exists in the conventional bridge-type voltage-source inverters. In order to solve the aforementioned problem, this paper proposes a two-switch dual-buck grid-connected inverter. The freewheeling current flows through the independent diodes instead of the body diodes of the switches, so reverse-recovery loss of the diodes can be reduced. Half of the power devices operate in high frequency; the others switch at grid period with zero-current switching. Moreover, uniploar modulation is used. The operating principle, design guidelines and example, and stability analysis are provided. The proposed inverter can be simplified to a current amplifier with hysteresis current control, so it is globally stable. Simulation and experimental results verify the theoretical analysis and satisfy IEEE Std. 929-2000. A comparison of a full-bridge inverter and the proposed inverter shows that the proposed inverter is more attractive in high-reliability applications. © 1986-2012 IEEE. Source

Tian C.,Yancheng Institute of Technology | Zhang L.,Umea University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

An inhomogeneous distribution of species density over physical space is a widely observed scenario in plankton systems. Understanding the mechanisms resulting in these spatial patterns is a central topic in plankton ecology. In this paper we explore the impact of time delay on spatiotemporal patterns in a prey-predator plankton system. We find that time delay can trigger the emergence of irregular spatial patterns via a Hopf bifurcation. Moreover, a phase transition from a regular spiral pattern to an irregular one was observed and the latter gradually replaced the former and persisted indefinitely. The characteristic length of the emergent spatial pattern is consistent with the scale of plankton patterns observed in field studies. © 2013 American Physical Society. Source

Yao Z.,Nanjing University of Aeronautics and Astronautics | Xiao L.,Yancheng Institute of Technology | Yan Y.,Nanjing University of Aeronautics and Astronautics
IEEE Transactions on Power Electronics | Year: 2010

This paper presents a novel seamless transfer of single-phase grid-interactive inverters between grid-connected and stand-alone modes. The grid-connected inverter should operate in grid-tied and off-grid modes in order to provide power to the emergency load during system outages. However, the grid current controller and the output voltage controller are switched between the two modes, so the outputs of both controllers may not be equal during the transfer instant, which will cause the current or voltage spikes during the switching process. The transfer between the two controllers does not exist in the proposed method. In grid-tied mode, the voltage controller is used for compensating the filter capacitor current, and the current controller is used to control the grid current. In stand-alone mode, the voltage controller is used to regulate the output voltage, whereas the output of the current controller is zero. With the proposed control method, the seamless transfer can be achieved between both modes, even in polluted grid voltage. The principle and realization conditions of the control methods at both modes are analyzed. The detailed process of the seamless transfer between the two modes is illustrated. Finally, the simulation and experimental results verify the theoretical analysis. © 2006 IEEE. Source

Luo J.,Yancheng Institute of Technology
Materials Letters | Year: 2012

Nanosized Nd-doped strontium ferrites, SrNd xFe 12-xO 19, with x = 0.0-0.5, were successfully prepared through a chemical coprecipitation process. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and vibrating sample magnetometer (VSM). Various parameters such as lattice constants (a and c) and crystallite size were calculated from the XRD data. The crystallite size was in the range of 28-39 nm. The specific saturation magnetization (M s) and the coercivity (H c) of strontium ferrites could be improved by substitutions of Nd 3+ ions on Fe 3+ ion basis sites. The M s revealed magnetic behavior with respect to Nd 3+ ion concentration, showing a decrease. The H c increased with increasing Nd 3+ ion concentration. © 2012 Elsevier B.V. All rights reserved. Source

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